/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *    PackageConstraint.java
 *    Copyright (C) 2015 University of Waikato, Hamilton, New Zealand
 *
 */
package weka.core.packageManagement;

/**
 * Abstract base class for package constraints. An example implementation might
 * be to encapsulate a constraint with respect to a version number. Checking
 * against a target in this case would typically assume the same package for
 * both this and the target.
 * 
 * @author Mark Hall (mhall{[at]}pentaho{[dot]}com)
 * @version $Revision: 44030 $
 */
public abstract class PackageConstraint {

    protected Package m_thePackage;

    /**
     * Set the package that this constraint applies to.
     * 
     * @param p the package that this constraint applies to.
     */
    public void setPackage(Package p) {
        m_thePackage = p;
    }

    /**
     * Get the package that this constraint applies to.
     * 
     * @return the Package that this constraint applies to.
     */
    public Package getPackage() {
        return m_thePackage;
    }

    /**
     * Check the target package against the constraint embodied in this
     * PackageConstraint.
     * 
     * @param target a package to check with respect to the encapsulated package and
     *               the constraint.
     * 
     * @return true if the constraint is met by the target package with respect to
     *         the encapsulated package + constraint.
     * @throws Exception if the constraint can't be checked for some reason.
     */
    public abstract boolean checkConstraint(Package target) throws Exception;

    /**
     * Check the target package constraint against the constraint embodied in this
     * package constraint. Returns either the package constraint that covers both
     * this and the target constraint, or null if this and the target are
     * incompatible.
     * 
     * @param target the package constraint to compare against
     * @return a package constraint that covers this and the supplied constraint, or
     *         null if they are incompatible.
     */
    public abstract PackageConstraint checkConstraint(PackageConstraint target) throws Exception;
}
